Sun following reflectors have previously been of parabolic form and have required the use of complex electronic sun position sensors and expensive servo-mechanisms to continuously track the sun's position. In a parabolic reflector, the image of the sun is fixed at the focal point on the axis of the reflector, requiring continuous angular movement of the reflector to retain the sun's image at the focal point.
The present invention avoids complexity and expense by the novel use of the optical properties of a reflector of spherical form. In a spherical reflector, the image of the sun at the focal point of the reflector can traverse a limited distance along the focal plane while the reflector remains fixed. The present invention utilizes this property of a spherical reflector by placing a novel combined heat sensor and thrust motor in the form of a sealed expandable metal bellows in the focal plane of the spherical reflector to one side of a fixed heat exchanger placed at the axial focal point of the reflector and supporting the heat sensor and thrust motor to rotate with the reflector, so that travel of the sun's image off the heat exchanger and on to the heat sensor while the reflector is stationary develops a motor thrust which is stored by compressing a spring. The stored energy is released when sufficient and is translated by a mechanism into an angular rotation of the reflector which quickly returns the sun's image to the heat exchanger. The fixed heat exchanger placed at the focal point absorbs heat during the time of travel of the sun's image across it, while the bellows is cooled and contracts and the storage mechanism resets during this time to be ready for a succeeding image restoring cycle. The novelty of the invention resides in the placement and use of a combined heat sensor motor, together with the use of an energy storage and thrust translating mechanism to accomplish the angular steering of a reflector of spherical form to periodically restore the position of the sun's image to the focal point after it periodically departs from that point. The heat of the sun is thus utilized in a novel way by the present invention to provide both error sensing and motive power for automatic image restoration which enables the heat of the sun to be usefully employed by keeping the sun's image focussed on a heat exchanger placed at the focal point of the reflector and connected by pipes to an associated water heating system.